A high voltage electromagnetic induction device, such as a power transformer or a reactor, typically comprises a lead-through device which is an electrically insulated elongated device having a conductor arranged along its central axis.
The lead-through device extends into the high voltage electromagnetic induction device through a wall of the high voltage electromagnetic induction device and connects with the internal electric components. The lead-through device thus provides electrical insulation between the conductor and the wall, which typically has a significantly different electric potential than the conductor of the lead-through device and the internal electrical components during operation. The lead-through device thus defines an interface between the internal electric components of the high voltage electromagnetic induction device and external electric components located outside the high voltage electromagnetic induction device, for example valves of a valve hall.
The conductor of the lead-through device is connected to the internal electric components inside the high voltage electromagnetic induction device, for example inside the turret. The turret is a structure mounted to or integrated with the tank of the high voltage electromagnetic induction device, and adapted to receive a lead-through device. An electrical insulation system is arranged to electrically insulate leading parts from the wall and other structures, including the connection between the conductor and internal electric components, e.g. windings. In order to increase the electric withstand strength of the electrical insulation system it is possible to utilize pressboard barriers which are shaped according to the profile of the lead-through device. The electrical withstand strength is increased because the oil duct outside the lead-through device is reduced in size.
WO2010060450 A1 discloses an example of such an insulation system. In particular, WO2010060450 A1 discloses a barrier arrangement for a cable having barriers arranged next to each other and disposed at prescribed distances from each other. By introducing an additional barrier element between the cable duct and the barrier arrangement, an additional radial oil segment is created, so that the permissible field strengths within the oil can be increased.